We report six cases of rabies (three confirmed, three suspected) in gray wolves (Canis lupus) representing 21% of the total wolf mortality in a 5 yr study (1987 to 1992) of radio-collared wolves in Algonquin Provincial Park, Ontario, Canada. Reports of rabies in wolves of the Great Lakes region of North America are rare, even though wolf populations have been studied extensively for almost 40 years. No cases have been documented in wild wolves on the U.S. side of the Great Lakes, whereas, in Ontario, 15 cases have been documented since 1960.